Textile bleaching process

ABSTRACT

THE INVENTION RELATES TO A PROCESS FOR CONTINUOUSLY BLEACHING A TEXTILE FABRIC PREIMPREGNATED WITH A BLECHING SOLUTION BY PASSING THE FABRIC THROUGH THE STORAGE ZONE IN SLIDING CONTACT WITH A REMOVABLE INERT FLUOROCARBON POLYMER SHEET WHEREIN CHEMICAL DEPOSITES AND THE FABRIC READILY PASS THROUGH SAID J-BOX WITH LITTLE OR NO ABRASION AND DISTORTION BEING ENCOUNTERED BY THE FABRIC.

Jan. 12, 1971 J, s'r 'rgn ETAL 3,554,685

TEXTILE BLEACHING PROCESS Filed June 27, 1968 2 Sheets-Sheet 2 MENTOR NEIL J. STALTER OZAO 6: M Lq/Ag r5 aYy-L? ME "United States Patent O 3,554,685 TEXTILE BLEACHING PROCESS Neil J. Stalter, Noithminster, Del., and Otho S. McCullers, Greenville, S.C., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware Continuation-impart of application Ser. No. 590,587, Oct. 31, 1966. This application June 27, 1968, Ser.

Int. Cl. D061 3/02 US. Cl. 8-111 8 Claims ABSTRACT OF THE DISCLOSURE CROSS-REFERENCE TO RELATED APPLICATION This is a continuation-in-part of SN. 590,587, filed Oct. 31, 1966, now abandoned.

BACKGROUND OF THE INVENTION Textile fabrics, in open-width or rope form, are subjected to various commercial operations such as scouring, bleaching, caustic treatment, desizing and similar operations. Continuous operations of these types usually involve the steps of impregnating or dampening the fabric with a treating liquor such as a bleach solution, heating the impregnated fabric with live steam and storing the heated fabric temporarily in a device such as a J-box, all such steps being carried out continuously on a continuously advancing strand of the fabric. J-box systems for carrying out such operations are described in US. Pats. 2,267,718 and 2,858,184. Such J-box systems are generally regarded as closed systems in that they are essentially closed to the surrounding atmosphere except for ports or openings for the entry and exit of the fabric. In addition, open system J-boxes are also utilized, for example, as described in US. Pat. 2,391,905.

In the continuous treatment of textile fabrics, especially in bleaching, it is common in practice to utilize these J-boxes for storing the fabrics during the preparation and bleaching periods. Fabric is continuously fed into the J-box and continuously removed at the exit end. The movement of the fabric through the J-box involves a sliding action of the fabric against the inner walls of the J-box, especially on the bottom interior wall of the J-box where most of the fabric weight is concentrated. This sliding action frequently results in serious problems in the operation of the J-box equipment and also with the fabrics being treated.

The equipment operation problems and fabric problems can arise when the fabric does not slide properly from the entrance to the exit of the J-box. This may result in tangling and knotting of the fabric so that it is very difficult to pull the fabric through the J-box. In some cases it may be necessary. to cut the fabric to untangle the mass in the box. This, of course, results in lost production and damaged fabric. a

In less extreme cases the fabric may move through the J-box and be pulled from the exit with only moderate difficulty. However, the fabric becomes distorted and abraded from contact with the inner surface of the J- box. This distortion and abrasion result in subsequent rejection and economic loss of the fabric. Much of the Patented Jan. 12, 1971 ice damage to the fabric cannot be observed until the fabric is dyed, and it is at this time that distortion marks, dye streaks, etc., become apparent.

Although the J-box is conveniently constructed of stainless steel having a relatively smooth inner surface, this surface becomes roughened in use and leads to the problems discussed above. Various chemical reagents, which are utilized in fabric treating solutions, have a tendency to precipitate and deposit on the fabric and/or on the sides and bottom of the J-box. Also, various calcium and magnesium salts precipitate out from solutions when hard water is used. These solid deposits create an abrasive action which injures the fabric. In bleaching operations, one of the primary causes of the roughened surface is silicate build-up from the sodium silicate normally used in bleach formulas. The silicate deposits on the fabric and/or on the J-box surface, brought about through evaporation and precipitation of the bleaching solution, are extremely hard, insoluble, rough and abrasive. If deposited on J-box equipment parts with which the fabric is in sliding contact, abrasions on the surface of the fabric occur. This causes most serious difiiculties in subsequent dyeing operations where uneven dyeings are produced. In some instances abrasion marks on the goods may be so pronounced as to make even white finished goods commercially less acceptable; and in severe cases, abrasion may actually lead to thread breaks in the fabric.

It is most desirable that the fabric or cloth slides easily through the J-box, especially around the curved section of the J-box. When good sliding prevails, the dyeing problems are minimized. Good sliding is an absolute must when processing knit goods in order to hold stretch to a minimum.

In the past, several means have been used in attempting to alleviate the problems associated with the roughened J-box surfaces. For example, it has been the practice of some textile mills to periodically shut down operation of the J-box and to grind the silicate deposits from the surface. The stainless steel surface of the l-box was then polished with fine abrasives to place the J-box in condition for continued operation. Obviously, such a procedure is time consuming and costly.

Another method is to circulate hot solutions of caustic soda through the J-box periodically to smooth the surface by removing the accumulated deposits. Where buildup of silicate deposits is severe, this is only a partial remedy to the problem and must be repeated frequently to be effective. In some textile mills a modification of this method is utilized in which two I-boxes are used alternatively for the bleaching step and the caustic step so that the caustic tends to maintain a smooth surface in both J-boxes. However, this method only has utility where two J-boxes are available and plant lay-out makes the alternating procedure feasible. In either case, the caustic procedures are time consuming and undesirable for the most etficient operation.

Another method which has been utilized to reduce the sodium silicate deposits involves adjusting the pH of the bleaching solution with various chemical reagents. For example, US. Pats. 2,740,689 and 2,820,690 use various phosphates to adjust the pH and stabilize the bleaching solutions. Additionally, various sequestering agents have been added to bleaching solutions to prevent the precipitation of calcium and magnesium salts. However, while these preventative measures are partially effective, they are not a complete solution to the problem caused by chemical deposits in the I-box operations.

Thus, it is apparent that serious problems in the operation of J-boxes have existed for many years. Although many attempts have been made to alleviate the problems relating to the roughness of the J-box, distortion and abrasion of fabrics, etc., no economical and acceptable solution to these problems has heretofore been discovered.

SUMMARY OF THE INVENTION The invention relates to a process for continuously bleaching a textile fabric preimpregnated with a bleaching solution comprising feeding a continuous length of said fabric into the entrance of a J-box which has a fabric storage zone and a fabric exit, passing the fabric through said fabric storage zone and through said exit, the improvement comprising passing said fabric through said storage zone in sliding contact with a removable inert fluorocarbon polymer sheet wherein chemical deposits and the fabric readily pass through said J-box with little or no abrasion and distortion being encountered by the fabric.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view, with certain parts cut away, of a J-box having. a removable inert fluorocarbon polymer sheet attached thereto and equipped to handle textile fabrics in the rope form;

FIG. 2 is an enlarged section view of the flange and bolt means which attaches the fluorocarbon polymer sheet to the I -box;

FIG. 3 is a plan view, with certain parts cut away, of a J-box having a removable inert fluorocarbon polymer sheet attached thereto and equipped to handle textile fabrics in the open-width form;

FIG. 4 is an enlarged section view of a fluorocarbon polymer sheet and means used to secure said sheet to the J-box.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawings, reference numeral 1 refers to a closed J-box of the general type described in U.S. Pat. 2,858,184. .l-box 1 comprises a long vertical leg 2, a relatively short upright leg 3 with fabric exit port 5, and intermediate curved section 4, a bonnet section 6 and a fabric entrance leg (chamber) 7 with fabric entrance port 8. Heating of the fabric is effected in bonnet 6 and fabric entrance leg 7, which together constitute the heating zone wherein the fabric strand 9 is contacted directly with the gaseous heating medium, e.g. steam. A heating medium means, distributor box 22, is present to distribute the heating medium evenly across the width of bonnet 6, which is considered to be the upper portion of the J-box. A more detailed description of a suitable heat distributor box and arrangement thereof is shown in U.S. Pat. 2,858,184.

Leg 2, section 4 and leg 3 of the J-box constitute the storage zone thereof wherein the heated fabric is stored temporarily to complete the action of the treating agent upon the fabric.

In bonnet 6 is positioned a fabric forwarding mechanism or means for continuously advancing the fabric, such as draw reel 11, indicated in the upper cut-away portion of FIG. 1, and means (not shown) for plaiting fabric strand 9 as it drops down from draw reel 11 into a compact pile or mass 10 in leg 2. A suitable mechanism for use in conjunction with draw reel 11 whereby an advancing strand of fabric in rope form is piled in a compact plaited form uniformly across the cross-section of leg 2 is shown in detail in the above-mentioned U.S. Pat. 2,858,184. Other piling and plaiting mechanisms, many of which are well known, may also be employed. Thus, U.S. Pat. 2,939,306 shows a plaiting mechanism for use in conjunction with a draw reel such as draw reel 11 when the J-box is intended to handle cloth in openwidth form. Draw rolls 23, located outside of the fabric exit, are addtional means for continuously advancing the fabric.

The interior walls of the J-box, 12 and 15. are gen:rally made of stainless steel. Interior wall 12 is referred to as the wall which forms the back and bottom of the J-box.

The curved section of interior wall 12 is referred to as the concave section of said wall while the curved section of interior wall is referred to as the convex section of wall 15. Item 13 is a removable inert fluorocarbon polymer sheet having a thickness of, for example, 0.02 inch and covers the entire width, lower portion, and curved section (concave section) of interior wall 12, from flange 14 to flange 16. This sheet of fluorocarbon polymer is attached to the J-box at flange 14. The manner in which the fluorocarbon polymer sheet 13 is attached is more clearly shown in FIG. 2. Bolt 17, nut 18, bolt and nut 21 hold stainless steel clamp 19 against the polymer sheet 13. The polymer sheet extends from between bolt 17, bolt 20 and clamp 19, through and around flange 14 to interior wall 12. Thus, a simple bolt and nut arrangement with a steel clamp is utilized to efliciently secure the fluorocarbon polymer sheet into place. In similar fashion, the other end of the sheet can be attached at flange 16, although this is not necessary for successful operation of the J-box and is not shown here.

In operation, the continuous fabric strand 9 is preimpregnated with a bleaching solution and the fabric strand is drawn through entrance port 8 by reel 11. Heating of strand 9 is effected by its direct contact with the gaseous heating medium, e.g., steam, in leg 7 and hood 6. As strand 9 drops down from draw reel 11, it is plaited in leg 2 by the action of any suitable plaiting mechanism so as to form a compact fabric pile 10 from which strand 9 is pulled by draw rolls 23 through exit port 5.

As strand 9 passes through the J-box, it comes into sliding contact with fluorocarbon polymer sheet 13. The polymer sheet provides a smooth, slippery surface over which strand 9 can slide. In addition, any deposits or precipitates, as they form also readily slide through the J-box with the fabric and create no significant abrasion problems. The fluorocarbon polymer sheet in this particular J-box is a copolymer of tetrafiuoroethylene and hexafluoropropylene. The sheet has been positioned to extend from flange 14 to flange 16 on wall 12 (which forms the back and bottom of the J-box) since this is where most of the fabric weight is concentrated. However, as discussed below, any length or width of fluorocarbon polymer sheet can be positioned to cover any area on any wall or walls of the J-box as desired.

FIG. 3 shows the use of a fluorocarbon polymer sheet in another type of J-box and a different means to attach or fasten said sheet. In this figure, open-width fabric 25 is preimpregnated with bleaching solution; then the fabric is heated as it passes through the fabric entrance port 26, entrance leg 27 and bonnet 28. Reference numeral 29 refers to rollers over which the fabric travels. After the heating section, the fabric travels through the fabric storage zone comprising leg 30, curved section 31 and leg 32 wherein it is stored temporarily in piled form (not shown in the drawing). Then the fabric is withdrawn through exit port 33.

In this J-box, the removable inert fluorocarbon polymer sheet 36 is crimped together with a sheet of stainless steel 35 which has a hooked upper end 38, to form a one-piece sheet which is hung over the stainless steel Wall 34 of the J-box. Wall 34 is a common wall to the entrance leg 27 and to leg of the fabric storage zone. FIG. 4 shows an enlarged view of how stainless steel sheet 35 and fluorocarbon polymer sheet 36 are rolled and crimped together to form a one-piece sheet. The stainless steel sheet and fluorocarbon polymer sheet are joined together to form crimp roll 37. This crimp roll is in a tightly compressed form so that the two sheets are securely bound together. Additionally, this compressed crimp roll is small in size and consequently does not occupy any significant area on wall 34. The length of the fluorocarbon polymer sheet extends through substantially all of the curved section of the J-box, but the sheet does not cover a small portion of the short upright leg which leads to the exit port of the J-box. In all other aspects, the J-box of FIG. 3 contains similar features and can be modified in the same manner as in the previously described J-box of FIG. 1.

The particular J-boxes shown in FIGS. 1 and 3 described above are not the only types of J-boxes which can be utilized in this invention. Any J-box can be lined with a fluorocarbon polymer sheet to provide an excellent sliding surface in that particular J-box. For example, the well-known closed system J-boxes described in US. Pat. 2,267,718 and US. Pat. 2,858,184, as well as the open system I-boxes, for example, as described in US. Pat. 2,391,905, can be lined with a fluorocarbon polymer. In addition, the J-box of FIG. 3 may also be used. However, the closed system J-boxes produce the best results and, consequently, are preferred. Also, a J-box utilizing a controlled heating system comprising air and steam, as described in US. Pat. 3,196,642, may be lined with a fluorocarbon polymer in accordance with this invention.

The solid polymers (resins) used to line the inside of J-boxes are of the fluorocarbon type. The fluorinated polymers are generally the most useful because of their inherent chemical inertness, resistance to oxidation, durability, toughness and anti-friction properties. Other natural and/or synthetic resins, such as waxes, polyethylene, polypropylene, polyamides, silicone-containing polymers and copolymers or vinyl copolymers, may be used but do not have all of the desired attributes for purposes of this invention. Fluorocarbon polymers having on the average of at least one fluorine atom per carbon atom, such as the Teflon tetrafiuoroethylene resins, are preferred. These polymers resist attack by the most corrosive chemicals, retain their strength when exposed to extreme temperatures, excel in providing electrical insulation and are so slippery that practically nothing sticks to them (low coefficient of friction). Examples of such polymers are disclosed by Joyce, US. Pat. 2,392,389; Bro et al., US. Pat. 2,946,763; and Harris et al., US. Pat. 3,132,123. Resinous polymers prepared from tetrafluoroethylene, tetrafluoroethylene and hexafluoropropylene, vinylidene fluoride and chlorotrifluoroethylene, and perfiuorovinyl ethers are representative of the preferred type of fluorocarbon polymer. An especially suitable polymer is a copolymer of hexafluoropropylene and tetrafluoroethylene having the respective hexafluoropropylene:tetrafluoroethylene proportions of from 30:70 to 90:10 percent by weight.

The fluorocarbon polymer sheets may be of any desirable thickness. Generally, the thickness of the fluorocarbon sheets can be of any size with the proviso that the sheet can follow the contour of the J-box and can be bent around the curved section of the J-box if the sheet is positioned in said curved section. As a matter of economics and practicality, a thickness range of from about 0.005 to about 0.5 inch has been found to be useful. However, while sheets having a thickness greater than 0.5 inch may be diflicult to work with and/or economically impractical, they are still within the scope of this invention. In a preferred embodiment of this invention, fluorocarbon polymer sheets having a thickness of from about 0.01 to about 0.25 inch are used. Sheets having a thickness within this range are sufliciently strong to be fastened in place by a desired means without danger of tearing and, additionally, are sufliciently flexible to conform to the shape of the J-box without difliculty. It has been found that a fluorocarbon polymer sheet of about 0.02 inch in thickness is extremely satisfactory and performs very efliciently for purposes of this invention since it is flexible, easily fastened into place and thick enough to withstand long periods of use.

The width of the sheet of fluorocarbon polymer can vary considerably and is usually determined by the size of the J-box. Generally, it is desirable to cover substantially all of the surface over which the fabric will travel. However, this statement is not intended to limit the width of the sheet since any width can be used. Of course, the greater the widh of fluorocarbon sheet, the greater is the ease with which the fabric slides through the J-box. In a preferred embodiment, a sheet having a width which covers all of the area of the wall which forms the back and bottom of the J-box (designated as wall 12 in FIG. 1) is utilized.

The length of the fluorocarbon polymer sheet can also be varied to produce the desired results. For example, the length of the fluorocarbon sheet may extend from the top of the J-box through the long vertical leg, the curved section, and the short upright leg, to the exit. In like manner, the length of the sheet may only extend through the curved part of the J-box. In a preferred embodiment, the fluorocarbon sheet is secured to the interior wall which forms the back and bottom of the J-box, from flange 14 to flange 16 in FIG. 1 of the drawings, another preferred embodiment is shown in FIG. 3 where the length of the polymer sheet extends through substantially all of the interior curved section (concave section) of the J-box, but the sheet does not cover a small portion of the short upright leg which leads to the exit port of the ]-box. In addition to being economical embodiments, these are very effective since the curved section is where most of the fabric weight and contact is concentrated and incurred. Thus, a skilled artisan can readily adjust the length of the fluorocarbon polymer sheet to attain maximum sliding action within an economically feasible range.

The number of J-box interior walls which may be lined with the fluorocarbon polymer sheet is also a matter of choice. Therefore, one, two, three or four interior walls of the J-box may be lined with the fluorocarbon sheets. However, it has been found that the desired characteristics may be obtained by placing one sheet on the interior wall which forms the back and bottom of the J-box (reference numerals 12 and 34).

The fluorocarbon polymer sheet may be fastened in place by any suitable means that will hold it in place firmly and securely throughout the textile processing operations which are carried out in a J-box. For example, heat bonding or cementing provide suitable means for fastening. However, a simple procedure which has been found entirely suitable for use in accordance with the invention is to fasten one end of the sheet at any desired section of the J-box by bolts, rivets or other mechanical means and slide the free end of the sheet down into the box so that, in effect, the sheet is hanging from the top of the box (FIGS. 3 and 4). Alternatively, the fluorocarbon polymer sheet may be bolted to a wall of the J-box by any suitable arrangement, for example, through a flange (FIGS. 1 and 2). It has been found that a sheet inserted in the J-box as in these embodiments yields all the advantages of the invention in providing an excellent sliding surface with no build-up of roughness or deposits of any kind to interfere with the necessary sliding of fabrics.

It has unexpectedly been discovered that the J-boxes of this invention have increased capacity in addition to the previously enumerated advantages. This unexpected discovery involves (1) increased storage capacity and (2) increased capacity to more effectively bleach. It has been found that as much as 25% or more, fabric can be stored and bleached in the J-boxes of this invention. Instead of the fabric being piled from the bottom of the J to the upper portion (e.g., leg 2) of the I-box, the fabric can now be piled from the entrance to the exit. This provides significant amounts of added storage space which was not utilized heretofore. It is theorized that the improved sliding surface, essentially free of chemical deposits, permits the fabric to squeeze together more compactly and slide through the entire J-box. Regardless of the reason or mechanism involved, a larger amount of fabric can be stored in J-boxes of this invention than in the prior 1- boxes which do not contain the fluorocarbon polymer sheet liner. Due to the increased storage capacity, the fabric remains in the J-box for longer periods of time. Consequently, more efficient and more effective bleaching is achieved. In the alternative, the J-boxes can be operated at a higher rate of speed and still bleach as good as the prior J-boxes due to the increased capacity. These highly novel and unexpected features of this invention are significant improvements over the prior art.

It will be obvious that various modifications and adaptations of the preferred embodiment of the invention may be made without departing from the scope and spirit of the invention. However, it is an essential and critical feature of this invention to utilize a removable inert fluorocarbon polymer sheet. The use of a solid, separate and distinct sheet (piece), as opposed to a coating or film, produces significantly superior results in J-box bleaching.

In addition, a disadvantage in having a coating rather than a sheet of polymer on the inside of the J-box would arise if the coating begins to show signs of tearing or cracking through normal wear and tear. The J-box cannot be discarded, but must be recoated with additional fluorocarbon polymer. This requires special surface preparation of the I-box in addition to the tedious operation involved in the actual coating process. This is in contrast to the preferred embodiment where a preformed sheet of fluorocarbon polymer is fastened to the inside of the ]-box. When the sheet becomes torn or cracked through normal wear and tear, it is merely removed, discarded and a new polymer sheet inserted. It is apparent from the foregoing that the preferred embodiment provides a more practical, eflicient and economical J-box which is easy to assemble, operate and repair.

One of the primary advantages of this invention is that any bleaching solution and any type of water (e.g., hard water) can be used. Common bleaching solutions, which contain hydrogen peroxide and sodium silicate, normally deposit large amounts of chemical precipitates on the fabric and damage the fabric. In addition, hard water causes salts of magnesium and calcium to precipitate. These common bleaching solutions and/ or hard water can be used in the process of this invention due to the improved sliding and cleansing action provided by the fluorocarbon polymer lined J-box. There is no need to add other stabilizing agents, sequestering agents, etc. to alleviate the chemical deposit problem, although such agents may be used if desired.

Generally, the bleaching solutions utilized in the process of this invention can contain the well known bleaching concentrations of hydrogen peroxide, sodium silicate, tetrasodium pyrophosphate, sodium polyphosphate, trisodium phosphate, sodium carbonate, sodium hydroxide, etc. A typical bleach formula (based on the weight of fabric) includes:

Percent H 100%) 0.2-1.2s Na SiO 0.5-3.0 NaOH O-2.0

N34P207 Na PO O-O.5 Nagco3 One of the major contributions of this invention is that the advantage of avoiding the formation of objectionable deposits connected with the use of phosphates as bleach bath stabilizers in steam bleaching operations is fully maintained. However, the disadvantages of low bath stability, low fabric brightness, lack of uniformity in bleach results and chemical fiber attack are avoided when the process of this invention is utilized.

The following examples are further illustrative of the invention and advantages thereof. However, these examples are not intended to limit the invention.

EXAMPLE 1 A bleaching solution was prepared containing 2.2% hydrogen peroxide (35%), 1.2% sodium silicate and 0.2% Alkanol HSC (sodium alkylaryl sulfonate), based on the weight of the fabric. The fabric in this example was vat-dyed colored yarn goods in rope form. The prepared fabric (desized and washed) was impregnated with the bleaching solution to the extent of moisture pick-up (100 g. of fabric contains 100 g. of bleaching solution).

A solid polymer sheet of a tetrafluoroethylenehexafiuoropropylene copolymer having a thickness of 0.02 inch was inserted in a peroxide bleaching J-box designed for bleaching fabric in rope form. The sheet was fastened at the lower portion of the J-box, designated as flange 14 in FIG. 1 and extended in length to flange 16. The width of the sheet extended across the entire width of wall 12. The J-box was then placed in continuous operation for peroxide bleaching. The preimpregnated fabric (described above) was placed in the J-box and steamed for one hour; this bleaching process was run continuously for ten months. At the end of this ten-month period no silicate deposits or other chemical deposits had built up in the J-box and/or on the fabric. The sliding characteristics between the fabric and the J-box were excellent throughout the ten-month period and said characteristics remained the same at the end of ten months as they were when the polymer sheet was initially inserted into the J-box.

In comparison, a fabric was bleached (as described above) in a conventional J-box similar to that in FIG. 1 except that no inert fluorocarbon polymer sheet was inserted therein. This conventional J-box operated for three weeks after which time difliculty was encountered in the operation of the J-box due to the build-up of silicate and other chemical deposits. The fabric showed severe signs of abrasion and distortion.

By way of contrast, a fiber glass sheeting was coated with a tetrafiuoroethylene-hexafiuoropropylene copolymer. This special fluorocarbon coated fiber glass sheet was used in place of the pure fluorocarbon polymer used above in the same manner and the same bleaching process. The fluorocarbon coated fiber glass sheet deteriorated in two weeks to the point where it could no longer be used.

EXAMPLE 2 A bleaching solution was prepared containing 3.2% hydrogen peroxide (35% 0.5% sodium hydroxide, 2.0% sodium silicate (42 B, 0.3% tetrasodium pyrophosphate and 0.2% Sandopan D.T.C. (ethylene oxide condensate containing anionic groups), based on the weight of the fabric.'The fabric in this example was poplin (50% cotton/50% polyester) in open-width form. The prepared fabric (desized and washed) was impregnated with the bleaching solution to the extent of 100% moisture pickup (100 g. of fabric contains 100 g. of bleaching solution).

A J-box, as described in FIG. 3 but without a fluorocarbon polymer sheet, was placed in continuous operation, at a constant rate of speed, for a Rapid Bleach process as described in US. Pat. 2,960,383. The preimpregnated fabric (described above) was placed in the J- box and steamed for '8 minutes. It was observed that the fabric was piled (stacked) from the midpoint in the bottom of the J to a point near the upper portion of the I-box. This Rapid Bleach process was run for three weeks. At the end of this three-week period, chemical deposits had built up in the J-box and on the fabric; the fabric showed signs of abrasion and distortion. This illustrates a bleaching process of the prior art.

EXAMPLE 3 A bleaching process in accordance with Example 2 was carried out, except that a solid polymer sheet of a tetrafluoroethylene-hexafluoropropylene copolymer, having a thickness of 0.02 inch, was inserted into the J-box. The sheet was fastened as in FIGS. 3 and 4.

It was observed that the fabric was piled (stacked) from a point near the entrance to a point near the exit of the J-box. Due to this increase in storage capacity, the

piled fabric was steamed for 10 minutes in the J-box; this produced a whiter and brighter fabric than the well known process of Example 2. Additionally, after installation of the fluorocarbon polymer sheet, the bleaching process operated with no problems connected with sliding of the fabric in the J-box or with chemical deposits. At the end of four months the fluorocarbon polymer sheet showed no deterioration and operation of the bleaching process was trouble free.

EXAMPLE 4 The process of Example 3 was carried except that the concentration of H was reduced to 2.8%. The bleached fabric was as white and bright as the bleached fabric of Exmaple 2 (without fluorocarbon polymer sheet) in spite of the reduced peroxide concentration. This is attributable to the increased storage capacity of a lined J-box whereby the bleaching time is increased from 8 to minutes while the bleaching process was carried out at the same rate of speed. Thus, this example demonstrates that a savings in hydrogen peroxide can be made without a sacrifice in whiteness and brightness when compared with conventional bleaching procedures.

Since the fiuorocarbon polymers are generally considered to have relatively poor abrasion resistance, it is somewhat surprising and unexpected that these polymers have been found to be effective in the process of this invention. Normally, fluorocarbon polymers become abraded from continual moving contact with other materials. How ever, in this particular application in J-boxes, no signs of abrasion have resulted to the fluorocarbon polymer sheet.

What is claimed is:

1. In a process for continuously bleaching a textile fabric preimpregnated with a bleaching solution comprising feeding a continuous length of said fabric into the entrance of a J-box which has a fabric storage zone and a fabric exit, passing the fabric through said fabric storage zone and through said exit, the improvement comprising passing said fabric through said storage zone in sliding contact with a removable inert fluorocarbon polymer sheet wherein chemical deposits and the fabric readily pass through said J-box with little or no abrasion and distortion being encounttered by the fabric.

2. A process in accordance with claim 1 wherein the bleaching solution, based on the weight of the fabric, comprises 0.2-1.25% hydrogen peroxide (100%) and 0.53% sodium silicate.

3. A process according to claim 1 wherein the inert fluorocarbon polymer sheet is a polymer selected from the group consisting of polytetrafiuoroethylene and polytetrafluoroethylene-hexafluoropropylene polymers.

4. In a process for continuously bleaching textile fabrics with a bleaching solution wherein said fabric is continuously moved from a supply station to a J-box and re moved, wherein the moving fabric is first impregnated Y with a bleaching solution containing a bleaching concentration of hydrogen peroxide, and the preimpregnated fabric thereafter steamed in the J-box until the fabric is bleached, the improvement comprising passing said fabric through the J-box in sliding contact with a removable inert fluorocarbon polymer sheet wherein chemical deposits and the fabric readily pass through said J-box with little or no abrasion and distortion being encountered by the fabric.

5. A process in accordance with claim 4 wherein the bleaching solution. based on the weight of the fabric, comprises 0.21.25% hydrogen peroxide and 0.5-3 sodium silicate.

6. A process in accordance with claim 4 wherein the bleaching solution, based on the weight of the fabric comprises 0.21.25% H 0 (100%); 05-30% Na SiO 0-2.0% NaOH, 00.5% Na P O- 0-0.57a Na PO and Na CO 7. A process according to claim 4 wherein the inert fluorocarbon polymer sheet is a polymer selected from the group consisting of polytetrafluoroethylene and polytetrafiuoroethylene-hexafiuoropropylene polymers.

8. A process for continuously bleaching textile fabrics preimpregnated with a bleaching solution comprising continuously feeding a continuous length of the fabric into the enclosed upper part of a J-box, continuously piling said fabric therein, continuously supplying steam into said enclosed upper part of the J-box and continuously passing said fabric through the J-box storage zone in sliding contact with a removable inert fluorocarbon polymer sheet wherein chemical deposits and the fabric readily pass through said J-box with little or no abrasion and distortion being encountered by the fabric.

References Cited UNITED STATES PATENTS 2,970,042 1/1961 Lagerwey 22063X 3,104,225 9/1963 Benedetto 220-63X 3,196,642 7/1965 Terhune et al. 68-5.4 3,335,758 8/1967 Bertolet 22063X 3,019,631 2/1962 Freyberg 68178 3,280.039 10/1966 Smolens 232186 3,353,903 11/1967 Potter et a1 8-111 3,411,328 11/1968 Fleissner 68-5 MAYER WEINBLATI, Primary Examiner US. Cl. X.R. 

